The invention relates to split frustoconic jaws designed for anchoring to retainer blocks cables such as those intended to produce pre-stressing in a concrete structure or to brace a bridge, these jaws being adapted to grip these cables and to coact with housings having at least one complementary frustoconic portion, said housings being hollowed from one side to the other in said blocks.
The jaws concerned are composed of two, three or four indentical elements--called "keys" below--each derived from an original part bounded externally by a frustoconic surface and hollowed by a cylindrical axial channel whose inner surface is advantageously scored, said original part being decomposed into said keys by sawing along two, three or four radial half-planes.
In known embodiments of the above jaws, the keys obtained by sawing are gathered in bulk.
Then they are subjected to a surface hardening heat treatment, and, to form a jaw, there are taken from the keys thus treated the required number--generally three--of the latter and they are assembled by means of an annular steel ring housed in a circular groove itself hollowed in the outer frustoconic surface of the original part, in the vicinity of its large base.
This assembly formula presents certain drawbacks and in particular the following.
By reason of the mixing in bulk of the keys between their fabrication by sawing and individual taking-up following the hardening treatment, the keys taken up to constitute each jaw do not generally come from the same original part.
This circumstance would be of no consequence if all the keys were strictly identical.
However this is not the case in industrial manufacture on a production scale since then the saw lines are not always strictly axial and radial and their mutual angular separations are not always strictly equal between them.
Thus the cutting out of the original part can present the sinuous shape visible at S in FIG. 1 or extend along planes inclined to the ideal radial planes, as visible at R in FIG. 2.
In this case, the gripping of the jaws concerned does not lead to perfect juxtaposition plane to plane of the lateral surfaces of contiguous keys: the juxtaposition of these keys reconstitutes a very imperfect cylindrical channel, with the formation of excessive and irregular spaces between the keys and possibly the creation of gaps at the level of their connections, which can generate high local stresses capable of causing the breaking or the slipping of the cables to be anchored.
To overcome this drawback, severe checks and manufacturing tolerances must be imposed, hence expensive for the manufacturer of the keys.
It is an essential object of the invention to overcome the drawback indicated in a particularly economical manner since it permits the checks indicated to be eliminated.